1. Technical Field
The present disclosure relates to a printer having a mechanism for mounting and moving a printhead on a carriage, and to a method of controlling the printer.
2. Related Art
Printers that convey sheet media over a platen surface, dispose the printhead mounted on a carriage above the platen surface, and have a carriage moving mechanism that moves the carriage carrying the printhead bidirectionally across the paper width (in the transverse direction) perpendicularly to the media conveyance direction are known from the literature. See, for example, JP-A-H08-156362. The printer taught in JP-A-H08-156362 has a home position detection sensor disposed within the range of carriage movement, detects the carriage at the home position by this sensor, and counts the number of steps a stepper motor is driven from this position to control the position of the carriage.
Some inkjet printers have a lift mechanism that raises and lowers the carriage carrying the printhead to hold the gap between the platen and the printhead to a constant distance. This configuration requires a mechanism that moves the carriage in two directions, across the paper width (horizontally) and up and down (vertically). When a large printhead such as a line inkjet head is used, the head unit including the printhead mounted on the carriage becomes accordingly large. As a result, precisely controlling the position when moving this head unit vertically and horizontally is difficult, the paper or other member may contact the printhead and become soiled with ink, and the printhead can be potentially damaged. Furthermore, if movement of the carriage or printhead stops because of some problem, recovery is difficult if the position where the carriage or printhead stopped is unknown, and the carriage or printhead may be moved in the wrong direction.
To precisely control the position of a head unit comprising a printhead mounted on a carriage, a detection mechanism that accurately detects the position of the carriage is desirable. For example, if an encoder or other sensor is mounted on the carriage, the position of the carriage can be detected throughout the full range of carriage movement. However, when the carriage moves in two directions, vertically and horizontally, two sets of encoders or other sensors must be disposed to the head unit, construction becomes complicated, the parts count rises, and the cost increases. Furthermore, because the number of parts mounted on the head unit increases and the head unit becomes even larger, moving the head unit at high speed becomes difficult and throughput drops.